Method of feeding dry-pulverized coal



Nov. 3 1925- W. E. TRENT METHOD OF FEEDING DRY PULVERIZED COAL Filed Oct. 22. 1919 HHHHHHH A TTORNE Y.

Patented Nov.- 3, 1925.

; I 1,559,810 PATENT OFFICE.

WALTER E. TRENT, OF WASHINGTON, DISTRICT OF COLUMBIA, "ASSIGNOR, BY MESNE ASSIGNMENTS, TO TRENT PROCESS CORPORATION, OF WILMINGTON, DELAWARE,

A conrnmnon' or DELAWARE.

m'mnon or FEEDING nmnronvn nxznn COAL.

Application filed October 22, 1919(- Serial No. 332,548.

To all whom it may concern:

Be it known that WALTER E. TRENT, a citizen of the United States of America, residing at Washington, inthe District of Columbia, has invented certain new and useful Improvements in Methods of Feeding Dry-Pulverized Goal, of which the follow- 'ing is a specification, i

The present invention relates to. a method of feeding materials in afine state of division, and although particularly adapted for the feeding of dry pulverized coal, it is capable of use in many other fields where it is desirable to feed a finely pulverized substance.

In the prior art methodsit has heretofore been the custom to-feed dry pulverized coal by mechanical means directly into a moving air current to be carried therein to a point of consumption. Methods. of this character are not adaptable for feedlng coal into generators operating under high internal pressures and are limited in use to boilers and furnaces operating under atmospheric pressure conditions.

The present invention comprises a method of feeding dry powdered coal dust continuously and uniformly under pressures of several hundred pounds to the square inch tov pressure generators, or to boilers and furnaces' under any desired pressures, elimimating the necessity of mechanical apparatus for metering the feeding of the fuel. I

It is a further object of the invention to provide a method of feeding dry pulverlzed coal which consists in introducing a quantity of coal dust to a closed receiver, and in then blowing or carrying the coal in suspension in-a fluid air current under pres-' sure from the receiver to aint of consumption. The air. in addition to acting as a vehicle for feeding the coal, also forms a part of the air necessary to support the ,combustion thereof, additional air as may be required being supplied at or near the point of combustion.

In following the present method, where coal is to be fed, a closed receptacle is supplied with a given quantity of finely powdcrcd coal dust and then the source of supply closed. Air is introduced to the closed rcreptzu-le at a higher velocity, preferably discharging downwardly upon the surface of a batch of coal creating air currents with ,moisture of the air.

n the receptacle to agitate or throw the dust 5 into the currents which carry the same entrained therein from the receptacle to a pointjwhere the coal is to be consumed. It ias been found that by introducing the air current to the receptacle at its upperportion 00 so that the same discharges downwardly upon the surface of the coal, it causes a uniform feeding of the dust without allowmg the coal left in the tank to absorb'the This manifestly pre-' vents the dust from becoming dam or' soggy, which condition may happen the air 1s blown upwardly, through the charge i of coal dust, thus stopping the feeding of the same from the tank before its entire 7 contents have been discharged. It has been found that the air stream entering the closed receptacle can be made to carry more coal dust than its supply of oxygen will cause to burn, so that the mix- 7 ture may be kept overrich and non-explosive during a superheating until additional air s introduced thereto at the point of burnmg. -The additional air necessaryto form the combustible charge is preferably also superheated and mixes ,with the -overrich mixture at or near the combustion chamber. It will, therefore, be seen that by having part. of thenecessary air of combustion carrying all of the coal dust, it is possible to handle the dust in a perfectly safe manner. while being superheated, which overrich mixture, after its heat treatment, is joined with a supply of heated air so that the ulti-- mate mixture at the point" of combustion will} consist of the proper ratio af air and coal dust. 4

In following the present method, while it has been found-preferable to introduce the air to a closed receptacle containing the batch of coal so as to discharge downwardly upon the surface of the mass, it will, of course, be understood that the air can be introd'uced to the bottom of the rece tacle' and allowed to pass up through the 0 large of coal dust carrying with it a determined quantity of coal, depending upon the pressure and velocity of the air. If the air is introduced to the receptacle in this manner, it is preferable to first pass the same throu h an apparatus to extract the moisture rom the air so that when the same enters the closed receptacle it will have no tendency to cause the mass of coal become damp or soggy, which conditioninterrupts, or stops, the coal feeding entirely.

. After the coal dust has left the'receptacle and I have disclosed in my copending ap plication, Serial Number 326,899, a highly eflicient apparatus for preheating both the air and fuel so as to render the fuel. highly combustible, and this form of apparatus is preferably employed in following the herein described .method.

In the accompanying drawings I have shown and described suitable apparatus capable of supporting the method, but it will be understood that many other forms of apparatus varying materially in structure may be used without departing from the spirit of this invention.

In the drawings Figure 1 represents a view of the apparatus with parts in section.

Figure 2 is a sectional view of the receiving tanks.

Referring now more particularly to the drawings wherein like reference characters indicate corresponding parts, the numeral 1 designates a main source of supply which is adapted to receive pulverized or finely divided material 2 that may be oal, reduced ore, or a mixture of ore and coal. If the material is coal, the same may have undergone a preliminary treatment so as to free it of its ash-forming substances as specified in my application, Serial Number 309,642,

Patent No.-1,420,163,-June 20, 1922, but itv will, of course, be understood that it is not entirely essential that the coal be cleaned in this manner before introduction to the suply bin 1, as finely pulverized co'al, such as 1s now usually burned, may be used for some purposes. Disposed within the body of the receptacle 1 is a screw feed conveyor 3, driven by the pulley 4 for discharging the coal through thefeed pipe 5 having communications 7 and 8 with the coal receiving receptacles 9 and 10, two of these receptacle bemg shown for the purpose of illustration, but manifestly any desired number of receptacles may be employed. Thecommuni'catlons 7 and 8 are controlled b the independently operable valves 11 and 12 so'that proper,manipulation of either of these- 'valves, a supply of coal dust maybe introduced to. single receptacle at the time, or

to both simultaneously.

When pulverized coal is to be" fed in its dry. state to a combustion conduit designated by the reference character 13, a portion of a generator and this conduit being disclosed in Figure l of the drawings, one or both receptacles '9 and 10 are preferably filled to the level indicated in the sectional showing in Figure 2, whereupon the supply valves 11 and12 are closed. I

Communicating with each of the receptacles 9 and 10 is an air feed pipe 14 leadingfrom any suitable source of supply and adapted to convey air under pressure to both of the receptacles. The pi'pe'14 has a branch pipe 15 communicating therewith and leading to the receptacle 9, while a similar branch pipe 16 leads to the receptacle 10.. Each branch pipe is controlled by one of the-independently foperable valves 17 and 18 so that the source of supply of air is under instant control, permitting the air 'a circular discharge nozzle 19 disposed with in the interior of this tank or receptacle, and provided with a plurality of jet openings 20' through which the fluid discharges.

Assuming that this tank has been filled to the level indicated in Figure 2 witha suppl of ma] dust, the valves 18 and 32 of the tank 10 are closed, and the valves 17 and 22 opened, causing a supply of air .to pass through the feed pipe 15, the jets in the 'nozzle19, and directly upon the surface of the coal in the tank 9 creating a disturbance therein due to the air currents within the closed receptacle. The coal is gradually carried away in these air currents, passing outwardly through the feed pipe 21 controlled by the opened valve 22 into the coil 23 extending around the combustion chamber andthen through the feed pipe 24 controlled by i the valve 25 .to the firing conduit 13, the mixture passing around the combustion chamber being superheated by the heat absorbed from the products. of combustion. Byhaving the feed nozzle 19 of a circular formation with a numberof spray openings in its under side, theentirecontents of the receptacle will be ra'dually discharged with the air without orming'irregular pockets or openings in the surface of the coal supply.

The quantity of air necessary to feed a given amount of 'dry pulverized coal' from the tank 9 is much less than the required volume of air necessary to supportcombus.

tion of this fuel. The mixture of air and coal passing through the discharge pipe 21' is therefore overrieh and will not burn when given a superheating, but to cause combustion at or near the combustion chamber, an

fuel. The apparatus by which the mixture of air and coal dust and pure air alone are heated is merely disclosed in section, but it will be understood that this apparatus forms the subject matter of another application, Serial Number 326,899, and is merely herein disclosed for the purpose of showing a highly efiicient means for placing the coal dust in condition for burning.

After the entire contents of the receptacle 9 have been dischargedby reason of the air currents, the valves 17 and 22 are closed and the valve 11 opened to admit an additional supply of finely divided coal thereto from the main supply bin 1. The valves 18 and 32 are then opened and air passes through the feed ipe 16 into the circular nozzle 30 shown in 'the lower portion of the tank lO'to discharge or feed a'batchof coal dust that has been deposited within this receptacle or tank. It will be observed that the air nozzle 30 is positioned in the lower portion of the tank which is distinguished from the position of the air nozzle 19 in the tank 9, but thisis merely an alternative form of introducing air to a receptacle when the same is sufliciently dry to permit feeding in this manner. It will be observed that the air entering the tank 10 is disclosed as passing through a filter or' air dryer 33 so as to extract orremove any moisture that the air may contain before itis introduced to the receptacle. The discharged air passing through the jet openings in the nozzle 30 rises through the mass of pulverized coal carrying a ortion thereof in suspension through the ischarge pipe 31 controlled by the valve 32 to the firing conduit 13 for burning, the proportion of air and coal being the same as described in connection with the feeding of the coal from to the tank 10 is continued until the entire contents of this tank or receptacle have been discharged, whereupon the air fed is shut off and by a proper manipulation of the valves, air is, again admitted to the tank 9 which has meanwhile received a su ply of-coal, it bein observed that the coal is fed intermittent y from one receptacle and then another.

As has been heretofore stated, it has been -the tank 9. The introduction of the air found that by introducing the air downwardly upon the surface of the supply of coal dust as disclosed in the tank 9, the dust has no tendency'to absorb the moisture of the air and thereby become damp or soggy. By feeding the air through the mass of coal from the bottom thereof, if the air is moist, it has a tendency to impart its moisture to the coal dust in the tank. However, when feeding in this manner, if the air is moist,

the same is preferably passed through the air dryer or filter 33 as disclosed in Figure 2 which may be of any of the well known air so that only dr air is admitted to the tank 10 by the nozz e 30.

Having thus described the invention, what I claim is:

A process for feeding pulverized coal in tinuing the introduction of air to such receiver andintroducing a stream of air to the second receiver under pressure dischargtherein to pass through said material to ward its surfaces, and to carry particles thereof in suspension, and in removing the moisture from said air before it .is introduced to said last-mentioned receiver.

In testimony whereof I aflix my signature.

V WALTER E. TRENT.

types to remove all the moisture from the ing into the lower'portion of the material 1 

